Friction stir welding method and friction stir welding tool

ABSTRACT

In a friction stir welding method for friction stirring and welding a material by using a rotating tool  2  having a shoulder  4  and a pin  5  at a front portion of a shaft portion  3  and injecting a cooling agent Ac from a cooling nozzle  11  to the tool to be cooled thereby, the cooling agent is injected to a middle portion in an axial direction of the tool  2  to thereby prevent thermal expansion in an axial direction of the tool.

The present application claims foreign priority from Japanese PatentApplication (P.2005-323888) filed on Nov. 8, 2005, the entire contentsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a friction stir welding method and afriction stir welding tool for welding a welded member of a metal platemember, an extruded member or the like by friction stirring the weldedmember.

2. Related Art

There is known a friction stir welding method for bringing a rotatingshaft-like tool into contact with a material, softening a welded portionof the material by friction heat, and welding by stirring (refer to, forexample, JP-T-07-505090).

JP-T-07-505090 discloses that by moving a probe (distal end portion) ofa rotating tool along a butting line while bringing the probe intocontact with butted portions of works butted to each other to carry outfriction stir, the butted portions are welded.

In addition, there is known a technology of preventing the material frombeing adhered to the tool by injecting a cooling agent to the distal endportion of the tool and the welded portion in the above-describedfriction stir welding (refer to, for example, JP-B2-3530342).

According to the technology of JP-T-07-505090, in the friction stirwelding, there is a case in which the tool is thermally expanded in anaxial direction by friction heat, the tool penetrates the welded member.In such a situation, not only an excellent welding state is not achievedin the friction stir welding but also there is a concern that the toolis butted to a back up member for backing up the welded member, adiesupporting theweldedmember or the like to destruct the tool.

According to the technology of JP-B2-3530342, although in order toprevent the material from being adhered to the tool by excessivefriction heat to retard a welding speed, in order to deprive excessiveheat, the cooling agent is injected to supply to the distal end portionand the welded face, when the cooling agent is applied to the tooldistal end portion, there is a concern that the friction heat is notsufficiently generated at the welded portion, the material is softenedinsufficiently, and an excellent friction stir welding state is notachieved.

SUMMARY OF THE INVENTION

Embodiments of the invention provide a friction stir welding methodcapable of carrying out excellent friction stir welding by preventingthermal expansion of a tool in an axial direction by effectively coolingthe tool while ensuring friction heat necessary for friction stirwelding at a tool distal end potion (pin and shoulder) and a toolpreferably used therefor.

In accordance with one or more embodiments of the invention, in afriction stir welding method for friction stirring and welding amaterial by using a rotating tool having a shoulder and a pin at a frontend portion of a shaft portion thereof and injecting a cooling agentfrom a cooling nozzle to the tool to be cooled thereby, the coolingagent is injected to a middle portion in an axial direction of the toolto thereby prevent thermal expansion in the axial direction of the tool.

In the friction stir welding method for injecting the cooling agent fromthe cooling nozzle to the tool to be cooled thereby, the cooling agentis injected to the middle portion in the axial direction of the tool,the thermal expansion in the axial direction of the tool is preventedand therefore, at a butted portion of the material or the like, atemperature drop of the shoulder of the front portion of the shaftportion and the pin of the front end portion related to friction stirwelding is small, the middle portion in the axial direction of the toolis cooled while ensuring friction heat necessary and sufficient forfriction stir welding. Therefore, elongation caused by the thermalexpansion in the axial direction of the tool can be prevented andexcellent friction stir welding can be carried out.

Further, the cooling agent may be injected from the nozzle by a flowvelocity of at least 160 m/second.

When the velocity of the cooling agent injected from the nozzle isconstituted by at least 160 m/second, the middle portion in the axialdirection of the tool can effectively be cooled and excellent frictionstir welding can be carried out.

Further, an axis line of the tool may direct in a vertical direction andan axis line of the injecting direction of the cooling nozzle may directin an upper direction and be inclined in the upper direction by 5°through 35° relative to a horizontal face.

When the axis line of the tool is directed in the vertical direction,and the axis line in the injecting direction of the cooling nozzle isdirected in the upper direction, and is inclined in the upper directionby 5° through 35° relative to the horizontal face, the middle portion inthe axial direction of the tool can effectively be cooled whilepreventing an influence of the cooling agent on the shoulder or the pinof the tool and excellent friction stir welding can be carried out.

Further, a sectional shape of an injection port of the cooling nozzlemay be long in an up and down direction and short in a transversedirection.

When the sectional shape of the injection port of the cooling nozzle isconstituted to be long in the up and down direction and short in thetransverse direction, the cooling agent is supplied along the axis linedirection of the tool, the middle portion of the tool can efficiently becooled, elongation of the tool caused by thermal expansion in the axialdirection can be prevented and excellent friction stir welding can becarried out.

Further, in accordance with one or more embodiments of the invention, afriction stir welding tool for friction stir welding used in a frictionstir welding method for friction stirring and welding a material byusing a rotating tool having a shoulder and a pin at a front portion ofa shaft portion thereof and injecting a cooling agent from a coolingnozzle to the tool to be cooled thereby, is provided with a groove inparallel with an axial direction on an outer peripheral face of theshaft portion.

The groove in parallel with the axial direction is provided at the outerperipheral face of the shaft portion of the tool and therefore, asurface area of an outer periphery of the tool can be increased by thegroove in the axial direction of the outer peripheral face, and alsowith regard to an efficiency of cooling the tool by the cooling agent,the efficiency of cooling the tool by the cooling agent can be increasedby increasing the surface area of the outer peripheral face of the tool.Further, the tool per se can be cooled by an operation of enlarging thesurface area even by rotating the tool, the efficiency of cooling thetool can further bye increased, elongation of the tool caused by thermalexpansion in the axial direction can be prevented and excellent frictionstir welding can be carried out.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1]

FIG. 1 is an explanatory side view showing a basic concept of frictionstir welding according to an embodiment of the invention.

[FIG. 2]

FIG. 2 is a view in an arrow mark 2 direction of FIG. 1 and is a view ofan end face of a cooling nozzle.

[FIG. 3]

FIG. 3 is a view showing the invention according to a friction stirwelding tool and is an explanatory side view similar to FIG. 1.

[FIG. 4]

FIG. 4 is a cross-sectional plane view of the tool shown in FIG. 3.

[FIG. 5]

FIG. 5 is a perspective view showing a modified embodiment of theembodiment of FIG. 1.

[FIG. 6]

FIG. 6 is a vertical sectional side view of FIG. 5.

[FIG. 7]

FIG. 7 is an explanatory side view of a modified embodiment of FIG. 1.

[FIG. 8]

FIG. 8 is an explanatory side view of a modified embodiment of FIG. 3.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Exemplary embodiments of the invention are explained as follows inreference to the attached drawings. Further, drawings are viewed in adirection of notation. FIG. 1 is an explanatory side view showing abasic concept of friction stir welding according to the invention, FIG.2 is a view viewing FIG. 1 in an arrow mark 2 direction, and is a viewof an end face of a cooling nozzle. Although according to theembodiment, there is shown an example of directing a front portion ofthe nozzle in an upper direction, as described later, an axis line of acooling agent injection port of the nozzle may be arranged to beorthogonal to an axis line of a tool and a cooling agent may be injectedto a middle portion of the tool.

A tool 2 is supported by a rotating tool holding piece 1 to be hung downtherefrom. The tool 2 includes a shaft portion 3 having a length in anaxial direction, includes a shoulder 4 in a shape of an inverse frustumof a cone at a front portion 6 of the shaft portion 3, and includes apin 5 having a small diameter at a front end portion of the shaftportion 3. Numeral 7 designates a welded member arranged on a backingplate 9, and a butt-welded portion 8 of the welded member 7 is subjectedto friction stir welding by rotating the tool 2 and moving the tool 2 inan arrow mark a direction relatively.

In friction stir welding, the pin 5 of the tool 2 is brought intocontact with the welded portion 8 to face, friction heat is generated byrotating the pin 5, and the butt-welded portion 8 of the welded member 7is welded by friction heat. By moving the tool in the arrow mark adirection, a welded portion 10 is formed on a rear side in a directionof moving the welded portion 8. The butt-welded portion of the weldedmember 7 is welded by friction stir as described above.

A nozzle 11 is arranged to inject a cooling agent to a rear side in thedirection of moving the tool 2 and blown to a middle portion in an axialdirection of the tool 2 in the above-described. In synchronism withmovement of the tool 2, the nozzle 11 is moved in the same direction(arrow mark a direction) integrally therewith, injecting to blow acooling agent, for example, cooling air to an outer peripheral face on arear side in a moving direction of the tool 2.

According to the nozzle 11, a middle portion through an upper portionthereof are extended in a skewed upper direction to be remote from thetool 2, a front portion 12 thereof is proximate to a rear face of thetool 2, directed in an upper direction in a bent V-like shape, and anaxis line C of an injection port 13 is directed in an upper direction.Specifically, the injection port 13 of the nozzle 11 is proximate toface a middle portion in an axial direction (middle direction in heightdirection) of the rear side in the moving direction of the shaft portion3 of the tool 2, the injection port 13 is opened to direct in an upperdirection at a middle portion in an axial direction of the shaft portion3 and is opposed to an outer peripheral face of a rear portion of amiddle portion in an axial direction of the shaft portion 3.

In the above-described, cooling air Ac is injected to blow from theinjection port 13 of the nozzle 11 to the middle portion in the axialdirection of the outer peripheral face of the rear portion of the shaftportion 3 of the tool 2 to directing an upper direction in friction stirwelding. A portion to which cooling air Ac is blown is disposed at aposition of a portion which is sufficiently remote from the weldedportion 10 which the pin 5, the shoulder 4 generating friction heat faceand at which the cooling air Ac is not blown to the welded portion 10.

By the above-described, the cooling air Ac is blown to the middleportion in the axial direction of the shaft portion 3 of the tool 2 tocool the shaft portion and restrains and prevents thermal expansion inthe axial direction of the tool 2. At this occasion, the cooling air Acflows to direct in the upper direction at the middle portion in theaxial direction of the shaft portion 3 of the tool 2 and therefore, aninfluence of an operation of the cooling air Ac for cooling a portionsubjected to friction stir welding can be prevented as less as possible.Therefore, in friction stir welding, smooth and excellent friction stirwelding can be carried out by preventing friction heat from beingdeprived as less as possible while cooling the tool.

In the above-described, according to the position of blowing the coolingair Ac to the tool 2, the position is preferably disposed 20 through40mm from the front portion of the pin 5, actually, a distance A in alength Al of the tool 2 from a surface of the welded portion 8 of thewelded member 7 to the cooling air Ac is preferably 20 through 40mm,when the cooling air Ac is blown to the portion in the upper direction,a portion of the tool to which the cooling air Ac is blown constitutesan upper side of the tool, and thermal expansion in the axial directionof the tool can be restrained. When the portion to which the cooling airAc is blown is disposed excessively on an upper side of the tool,thermal expansion of the tool in friction stir welding cannot berestrained and therefore, the above-described range is preferable.

Next, with regard to an angle of inclination of the injection port 13 ofthe nozzle 11 directed in the upper direction, it is preferable that theaxis line of the shaft portion 3 of the tool 2 is directed in a verticaldirection, and each 0 made by the axis line C of the injection port 13and a horizontal plane C1 orthogonal to the axis line of the tool 2falls in a range of 5° through 35° at the above-described distance A of20 through 40 mm. θ is particularly preferably 20°.

When θ is equal to or larger than 5°, a possibility that cooling air isblown to the heated welded portion is low, and an influence on a distalend portion (a heated portion of the pin, the shoulder or the like aswell as a welded portion subjected to friction stir) of the tool by thecooling air can be prevented. When θ exceeds 35°, an amount of flow ofthe cooling air blowing to an upper side in the axial direction of thetool is increased and a cooling effect is reduced. Therefore, theabove-described angle is preferable. Further, when θ is less than 5°,there is also a possibility that the flow of the cooling air blown tothe tool 2 is directed to a lower side, in this case, there is a concernthat the cooling air flows to the distal end portion of the tool, thereis a possibility of depriving friction heat and therefore, the angle ispreferably equal to or larger than 5°.

Next, with regard to a size of the injection port 13 of the nozzle 11,it is preferable that the size is smaller than a diameter of a sectionof the tool 2. For example, according to the embodiment, whereas anouter diameter of the shaft portion 3 of the tool 2 is 12 mm, an innerdiameter of the injection port 13 is set to long diameter 7 mm×shortdiameter 1.5 mm. Since the diameter of the injection port 13 is smallerthan the outer diameter of the tool, the cooling air is firmly blown tothe tool 2 and the tool can efficiently be cooled.

Further, with regard to the injection port 13, as shown by FIG. 2, avertically long shape is preferable. That is, an elliptical shapeconstituting a long diameter by the axial direction of the tool 2 andconstituting a short diameter by the width direction of the tool ispreferable. A vertically long rectangular shape having rounded fourcorners is also preferable. A ratio of a longitudinal length (H) to atransverse length (W) of an inner diameter portion of the injection port13 is set to, for example, 7:1.5.

Next, with regard to a flow rate of the cooling agent, the following ispreferable. For example, when cooling air of, for example, 100×10⁻³through 130×10⁻³m³ (100 liters through 130 liters) per minute is blownto the tool 2 having an outer diameter of 12 mm by using the injectionport 13 having H of 7 mm and W of 1.5 mm, thermal expansion of the toolcan be confined to an allowable range.

Next, a flow velocity V of the injection port 13 will be calculated. Theflow velocity V can be calculated by (flow rate Q/sectional area S). Theflow rate Q is (100×10⁻³ through 130×10⁻³)/60 (m³/second) and thesectional area S is (7×10⁻³×1.5×10⁻³)=10.5×10⁻⁶m². As a result, bycalculating the flow rate V=Q/S=(100×10⁻³ through 130×10⁻³)/(60×10.5×10⁻⁶)=(100 through 130)/0.63=159 through 206 (m/second), the preferableflow velocity of the cooling agent is 160 through 200 (m/second). Thatis, the flow velocity of the cooling agent may be at least 160 m/second,the flow rate is preferably as fast as possible, and may exceeds 200m/second.

Although as described above, an explanation has been given such thataccording to the embodiment, the cooling agent is constituted by coolingair, the cooling agent may be a liquid of cooling water or the like. Ina case of a liquid, a specific weight thereof is significantly largerthan that of a gas and a cooling function is high and therefore, theflow velocity can be made to be low. With regard to the preferable flowrate of the cooling agent and the preferable flow velocity of thecooling agent described above, the same goes also in an example ofarranging the axis line of the cooling agent injection port of thenozzle mentioned later orthogonally to the axis line of the tool andinjecting the cooling agent to the middle portion of the tool.

FIG. 3 and FIG. 4 are views showing the invention according to afriction stir welding tool, FIG. 3 is an explanatory side view similarto FIG. 1 and FIG. 4 is an explanatory cross-sectional plane view of thetool. In the drawings, portions the same as the above-described areattached same notations and detailed explanation there of will beomitted. According to the invention, the plurality of pieces of grooves120 . . . in an axial direction are formed radially at an outerperiphery of a shaft portion 103 of a tool 102. The grooves 120 . . .are formed linearly in the axial direction from a middle upper portionof the shaft portion 103 to a front portion thereof or in front of theshoulder 4 in parallel with an axis line.

According to the grooves 120 . . . , as shown by FIG. 4, a width 121 ina diameter direction is set to be short, a side 122 in a circumferentialdirection in a direction following a direction of rotating the toolindicated by an arrow mark is set to be long to thereby set surfaceareas of the grooves 120 . . . to be large. Thereby, the surface area ofthe outer periphery of the tool 102 is widened, as a result, the toolper se can be cooled by an operation of enlarging the surface area evenby rotating the tool 102. In this case, the direction of rotating thetool is constituted by an arrow mark direction, and the side (wall) 122in the direction of rotating the tool 102 is exposed to wind blowing atthe outer periphery of the tool. Further, as described above, byinjecting to blow the cooling agent of cooling air or the like by thenozzle 11, the cooling operation is further promoted, theabove-described cooling operation can further be promoted, and thermalexpansion of the tool can be restrained further effectively and furtherefficiently.

FIG. 5 is a perspective view showing a modified embodiment of theembodiment of FIG. 1, FIG. 6 is a vertical sectional side view of FIG.5. In the drawings, numeral 2 designates the tool, numeral 3 designatesthe shaft portion, numeral 4 designates the shoulder, numeral 5designates the pin. Press metals 220, 220 for pressing vicinities of abutt-welded portion (welded portion 210) of welded members 207, 207arranged on the backing plate 9 press to hold the vicinities of thewelded portion by press leg portions 221, 221 arranged opposedly. Thewelded portion 210 of the welded members 207, 207 faces between endportions of the press metals 220, 220 opposed to each other, the distalend portion of the tool 2 faces between the end portions, and operationof friction stir welding is carried out.

Insides of the above-described press metals 220, 220 are provided withinjection ports 213, 213 of the cooling agent to open to end faces 222,222 opposed to each other. The injection ports 213, 213 are communicatedwith paths 211, 211 constituting nozzles provided at insides of thepress metals 220, 220, and inject to blow the cooling agent suppliedfrom a cooling agent supply source to the middle portion of the shaftportion 3.

Meanwhile, as clearly shown in FIG. 6, the paths 211, 211 constitutingthe nozzles are set to be opposed to each other and to be inclined inupper directions, and the injection ports 213, 213 are provided to beinclined in upper directions by an angle θ. The angle inclined in theupper direction of a front end of the path of the injection port issimilar to the above-described. In this way, the cooling agent may beinjected to blow to the tool by providing the cooling agent paths atinsides of the press metals used in subjecting the butted portions ofthe welded members to friction stir welding and opening the injectionports of the cooling agent to the end faces of the metal plates opposedto the tool.

FIG. 7 is an explanatory side view showing an embodiment of injectingthe cooling agent to the middle portion of the tool by arranging theaxis line of the injection port of the cooling agent of the nozzle to beorthogonal to the axis line of the tool. A cooling agent injection port23 of a nozzle 21 faces the outer periphery of the tool 2 and theperiphery of the middle portion of the length in the axial direction byproviding a predetermined gap therebetween, a front portion 22 of thenozzle 21 is directed in a horizontal direction, an axis line C3 of thecooling agent injection port 23 is directed in the directionsubstantially orthogonal to an axis line C2 directed in the verticaldirection of the tool 2, and the axis line C3 of the cooling agentinjection port 23 is substantially horizontal. The cooling agentinjection port 23 is opposed to the middle portion in the lengthdirection of the shaft portion 3 of the tool 2.

The flow rate and the flow velocity of the cooling agent are similar tothose of the above-described even in the embodiment of arranging theaxis line C3 of the cooling agent injection port 23 of the nozzle 21 tobe orthogonal to the axis line C2 of the tool 2 and injecting thecooling agent Ac to the middle portion of the shaft portion 3 of thetool 2 as described above, when the same flow rate and the same flowvelocity of cooling air is blown thereto, thermal expansion of the toolcan be confined in the allowable range.

FIG. 8 shows a modified embodiment of the embodiment of FIG. 3 mentionedabove, the plurality of pieces of the grooves 120 . . . in the axialdirection are radially formed at the outer periphery of the shaftportion 103 of the tool 102, a front portion 112 of a nozzle 111 isdirected substantially in the horizontal direction, and an axis line ofa cooling agent injection port 113 is directed in a directionsubstantially orthogonal to an axis line of the tool 102 directedsubstantially in the vertical direction.

Also in the embodiment, a cooling agent is injected to supply to themiddle portion in the axial direction of the tool 102 provided with thegrooves 120 . . . at the outer periphery, the surface area of the outerperiphery of the tool 102 is widened similar to the above-described bythe grooves 120 . . . , even by rotating the tool 102, the tool per secan be cooled by the surface area enlarging operation, the side (wall)122 in the direction of rotating the tool 102 is exposed to wind blowingat the outer periphery of the tool, by injecting to blow the coolingagent of cooling air or the like by the nozzle 111, the coolingoperation is further promoted, the above-described cooling operation canfurther be promoted, and the thermal expansion of the tool can berestrained further effectively and further efficiently.

Although an explanation has been given of the invention in details inreference to the specific embodiments, it is apparent for the skilledperson that the invention can variously be changed or modified withoutdeviating from the spirit and range of the invention.

1. A friction stir welding method for friction stirring and welding amaterial by using a rotating tool having a shoulder and a pin at a frontend portion of a shaft portion thereof and injecting a cooling agentfrom a cooling nozzle to the tool to be cooled thereby, the frictionstir welding method comprising: injecting the cooling agent to a middleportion in an axial direction of the tool.
 2. The friction stir weldingmethod according to claim 1, wherein the cooling agent is injected fromthe nozzle by a flow velocity of at least 160 m/second.
 3. The frictionstir welding method according to claim 1, wherein an axis line of thetool is directed in a vertical direction, and an axis line of theinjecting direction of the cooling nozzle is directed in an upperdirection and is inclined in the upper direction by 5° through 35°relative to a horizontal face.
 4. The friction stir welding methodaccording to claim 1, wherein a sectional shape of an injection port ofthe cooling nozzle is long in an up and down direction and short in atransverse direction.
 5. A friction stir welding tool used in a frictionstir welding method for friction stirring and welding a material byusing a rotating tool having a shoulder and a pin at a front portion ofa shaft portion thereof and injecting a cooling agent from a coolingnozzle to the tool to be cooled thereby, the friction stir welding toolcomprising: a groove provided on an outer peripheral face of the shaftportion and in parallel with an axial direction of the shaft portion. 6.A friction stir welding apparatus comprising: a rotating tool having ashoulder and a pin at a front portion of a shaft portion thereof; and acooling nozzle for injecting a cooling agent to the tool to be cooledthereby; wherein an axis line of the tool is directed in a verticaldirection, and wherein an axis line in an injecting direction of thecooling nozzle is directed in an upper direction and is inclined in theupper direction by 5° through 35° relative to a horizontal face.
 7. Thefriction stir welding apparatus according to claim 6, wherein asectional shape of an injection port of the cooling nozzle is long in anup and down direction and short in a transverse direction.